I13 = I23 = R2016 + O(R40) .

Note that by including the above dipoles we account for initial-state radiation at NLL accuracy, as an expansion in powers of the jet radius.
Higher order terms in the jet radius expansion can be computed, but in addition to the
suppression in \(R^2_0\)  the corresponding coefficient drops rapidly, and even for
\(R_0=1\)  the first terms are an appropriate approximation
[1]}.
<FIGURE>